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 ###Instrução: Quantos Liquidat (c) têm um propósito de composição dupla (máquina e manual)?
 ###Tabelas: CREATE TABLE proportions (proportions_id AUTO_INCREMENT PRIMARY KEY, Benchmark VARCHAR, Crown height VARCHAR, Pavilion depth VARCHAR, Table diameter VARCHAR, Girdle thickness VARCHAR, Crown angle VARCHAR, Pavilion angle VARCHAR, Brilliance Grade VARCHAR) CREATE TABLE overlap_between_multiple_social_network_services (overlap_between_multiple_social_network_services_id AUTO_INCREMENT PRIMARY KEY, Site VARCHAR, Bebo INT, Facebook INT, Friendster INT, LinkedIn INT, MySpace INT, Ning INT, Orkut INT, Plaxo INT) CREATE TABLE matches_and_goals_scored_at_world_cup_and_olympic_tournaments (matches_and_goals_scored_at_world_cup_and_olympic_tournaments_id AUTO_INCREMENT PRIMARY KEY, Match VARCHAR, Date VARCHAR, Location VARCHAR, Lineup VARCHAR, Result VARCHAR, Competition VARCHAR) CREATE TABLE clausura_2008_standings (clausura_2008_standings_id AUTO_INCREMENT PRIMARY KEY, Place (Posición) INT, Team (Equipo) VARCHAR, Played (PJ) INT, Won (PG) INT, Draw (PE) INT, Lost (PP) INT, Goals Scored (GF) INT, Goals Conceded (GC) INT, +/- (Dif.) INT, Points (Pts.) INT) CREATE TABLE alloys_for_mechanical_composition (alloys_for_mechanical_composition_id AUTO_INCREMENT PRIMARY KEY, Sn/Sb (%) VARCHAR, Liquidat (°C) INT, Solidat (°C) INT, Hardness ( Brinell ) INT, Purpose VARCHAR)  
SELECT COUNT Liquidat (°C) FROM alloys_for_mechanical_composition WHERE Purpose = dual (machine & hand composition)